1. Field of the Invention
This invention relates in general to a method of repositioning teeth for use in orthodontic treatment. Particularly, this invention relates to the use of orthodontic appliances for producing tooth movements. More particularly, this invention relates to the use of a plurality of elastic repositioning appliances for producing such tooth movements.
Orthodontic treatments involve repositioning misaligned teeth and improving bite configurations for improved cosmetic appearance and dental function. Repositioning teeth is accomplished by applying controlled forces to the teeth over an extended period of time. This is conventionally accomplished by wearing what are commonly referred to as “braces.” Braces comprise a variety of appliances such as brackets, bands, archwires, ligatures, and O-rings. After they are bonded to the teeth, periodic meetings with the orthodontist are required to adjust the braces. This involves installing different archwires having different force-inducing properties or by replacing or tightening existing ligatures. Between meetings, the patient may be required to wear supplementary appliances, such as elastic bands or headgear, to supply additional or extraoral forces.
Although conventional braces are effective, they are often a tedious and time consuming process requiring many visits to the orthodontists office. Moreover, from a patient's perspective, they are unsightly and uncomfortable. Consequently, alternative orthodontic treatments have developed. A particularly promising approach relies on the use of elastic positioning appliances for realigning teeth. Such appliances may comprise a thin shell of elastic material, referred to as an “aligner”, that generally conforms to a patient's teeth but is slightly out of alignment with the initial tooth configuration. Placement of an aligner over the teeth applies controlled forces in specific locations to gradually move the teeth into the new configuration. Repetition of this process with successive appliances comprising new configurations eventually move the teeth through a series of intermediate arrangements to a final desired arrangement. A full description of an exemplary elastic polymeric positioning appliance is described in U.S. Pat. No. 5,975,893, and in published PCT application WO 98/58596 which designates the United States and which is assigned to the assignee of the present invention. Both documents are incorporated by reference for all purposes.
Systems of preformed aligners employing technology described in U.S. Pat. No. 5,975,893, are commercially available from Align Technology, Inc., Santa Clara, Calif., under the tradename Invisalign® System. Align Technology, Inc., is the assignee of the present application. The Invisalign® System relies on designing and fabricating at least most of the aligners to be worn by the patient at the outset of treatment. The design of the aligners relies on computer modeling of a series of successive tooth arrangements, and the individual aligners are designed to be worn over the teeth and to elastically reposition the teeth to each of said tooth arrangements. Usually, the set of aligners which is designed and fabricated at the outset of the treatment is able to successfully reposition the teeth to a final desired arrangement. In some cases, however, the treatment deviates from the planned movement stages making continued treatment with the previously provided set of aligners difficult or impossible. Such deviations can arise from biological variations in the individual patient, poor patient compliance, or other factors. The deviations will usually become apparent when the next aligner to be worn in the set of successive aligners does not fit. A poor fit indicates that the tooth arrangement has not progressed to the desired intermediate stage and that the teeth are not ready for the next aligner.
When such deviations occur, the response has usually been to start over with whatever actual tooth arrangement that has been received being the starting point. Aligners are then planned and fabricated to bring the teeth from the actual intermediate arrangement to the desired final arrangement, which is usually the same final arrangement as was the target of the original set of aligners. Starting over, however, can be inefficient and wasteful. Relatively large numbers of aligners can be required, and the remaining aligners in the original set will usually be wasted.
For these reasons, it would be desirable to provide alternative and/or improved methods for making mid-course corrections in orthodontic treatment utilizing sets of aligners or other repositioning appliances which are removable and successively worn by a patient to effect a course of orthodontic treatment. It would be particularly desirable if such methods did not require disposal of all or some of the aligners from the original set and were relatively easy to implement with minimum patient inconvenience. At least some of these objectives will be met by the inventions described hereinafter.
2. Description of the Backpround Art
U.S. Pat. No. 5,975,893, and published PCT application WO98/58596, have been described above. U.S. Pat. No. 6,454,565, relates to the fabrication of orthodontic aligners having varying elastic moduluses. The full disclosures of each of these patents and pending applications are incorporated herein by reference.